News

Nutrient value of digestates

Published 28 February 14

Recognising a growing interest in anaerobic digestion and an increase in the production of digestate, the new MANNER-NPK software can now provide farmers with an estimate of crop available nitrogen, potash and phosphate from three different categories of digestates.

In a new DairyCo video, Nutrient value of digestate, Dr Lizzie Sagoo, from ADAS, looks at the nutrient value and regulations around the spreading of digestate.

Liquid digestate from anaerobic digestors just processing animal waste can be applied to land in the same way as livestock manure. When the digestor processes additional feed stock, such as food waste, as long as the digestate is PAS 110 compliant, it’s classed as a product not a waste and again can be applied to the land as you would a livestock manure.

Digestion of livestock slurry reduces the dry matter content and increases the proportion of readily available nitrogen. It won’t change the amount of total nitrogen, potash or phosphate in the slurry.

Because of its high levels of readily available nitrogen, digestate cannot be applied to the land during the NVZ closed period. In order to make the best use of this nitrogen, digestate should be applied when the plant is actively growing in the spring to summer period. As with any slurry application, using a trailing shoe or shallow injector will reduce ammonia emissions and odour.

The three new digestate categories included in MANNER- NPK are:

Whole food-based digestates

Whole pig slurry-based digestate

Whole cattle slurry-based digestate

The programme also estimates what the digestate is worth in saved fertiliser costs.